Electronic displays are provided in many contexts to electronically render digital information to a viewer. The electronic displays receive information, and render the information through lighted cells in patterns that reflect the texts and pictures employed to convey the information.
A Head-Up Display (HUD) allows a viewer to view not only the lighted information, but due to the transparent nature of the HUD, the view through the HUD. Thus, a viewer may be delivered information while not losing the ability to view the real world through the HUD.
HUDs are implemented in a variety of contexts, and more commonly in the vehicle. The HUD may be implemented in a variety of surfaces and windows, for example, the front windshield. Thus, when a driver/occupant is in a vehicle, content may be displayed to the driver/occupant on the front windshield accordingly.
While a conventional HUD (simply called HUD) features a virtual image displayed at a close distance to the driver and display car related information such like speed, speed limit and icons, an augmented reality (AR) HUD features others virtual images which are then perceived as within the scene the user is seeing. It is thus possible to build a system combining both close and far virtual images which from multiple light generating sources on a single HUD display. With such system, primary content may be generated from a first source, and secondary content (used for augmented reality, that is to say to augment the real-world) may be generated from a second source.
FIG. 1 illustrates an AR HUD implementation 100, employed in a front portion of a vehicle cockpit. As shown, a viewer 150 gazes via the viewer 150's eyes 151 through a front windshield 110. Employing the capabilities of such an AR HUD, the viewer 150 is able to see two distinct virtual images, virtual image 101 and virtual image 102. Virtual image 101 may be employed to present a static set of information, for example, real-time and dynamic updates with various vehicular operations. Virtual image 102 may be employed to augment objects visible through the front windshield 110.
FIGS. 2-4 illustrate various system-level views of AR HUD implementations employing a beam splitter. Each of the AR HUDs shown implements a different beam splitter.
Referring to FIG. 2, a system-level implementation of an AR HUD 200 is shown. Referring to the system-level implementation, a first picture generating unit (PGU) 210 and a second PGU 220 are shown. A PGU may be any sort of image display source capable of generating a source image to ultimately be displayed via the AR HUD 200. For example, the PGU may be a semiconductor-based display, such a liquid crystal display (LCD) or organic light emitting display (OLED), receiving an image or instructions to render a lighted image from a microprocessor or programmable logic device.
As shown in FIG. 2, a source image is projected from the PGU 210 to a mirror 230, which reflects the source image to a beam-splitter 240. After which, the source image from the PGU 210 is reflected from the beam-splitter 240 to a mirror 250, which is then projected onto the front windshield 100, to be rendered viewable by a viewer 150's eyes 151.
Also shown in FIG. 2 is an optical path generated through a PGU 220. This optical path 220 is projected through the beam-splitter 240, reflected off mirror 250, and projected to front windshield 100, and shown to the viewer 150's eyes 151. The concept shown in FIG. 2 employs a beam-splitter 240.
FIG. 5 illustrates how a beam-splitter works through exemplary beam-splitter 500. As shown, light 510 and 520 each are reflected off a surface of the beam-splitter 500. As shown in FIG. 5, source light 510 divides into two light beams 511 and 512, and source light 520 divides into two light beams 521 and 522. Thus, employing a beam-splitter 240 in an AR HUD 200 allows two distinct images to be combined together.
FIG. 3 illustrates another system-level implementation of an AR HUD 300. As shown, the difference between AR HUD 300 and AR HUD 200 is the employment of beam splitter 310. FIG. 6(a) illustrates a side-view of the beam-splitter 310, illustrating each individual element employed to construct beam-splitter 310.
As shown, beam-splitter 310 includes two layers, a reflective coating 610 and a transparent substrate (either glass or plastic) 620. The provision of the reflective coating allows the reflectivity of the beam-splitter 310 to be improved, thereby allowing light 601 to be effectively reflected off the surface of reflective coating 610.
However, both of AR HUDs 200 and 300 facilitate light from PGU 220 reflecting backwards, and thus, interfering with a signal being employed to project onto a windshield surface. FIG. 4 illustrates another system-level implementation of an AR HUD 400. As shown, the difference between AR HUD 400 with AR HUDs 200 and 300 is the employment of beam splitter 410. FIG. 6(b) illustrates a side-view of the beam-splitter 410, illustrating each individual layer employed to construct beam-splitter 310. As shown, an anti-reflective coating layer 630 is provided on the rear surface of the transparent substrate 620. Thus, light projected via light path 602 is prevented from reflecting back to an originating source, and thus interfering with the light generation associated with projecting light path 602.